1. Field of the Invention
This invention relates to a leadframe for making semiconductor devices of the type which comprises a multiplicity of leads extending out from all sides of a resin package. The present invention also relates to a semiconductor device which is rode by using such a leadframe.
2. Description of the Related Art
A leadframe of the above-described type is known from Japanese Patent Application Mid-open No. 60(1985)-121747. For the convenience of description, reference is now made to FIGS. 3 and 4 of the accompanying drawings which show a typical example of such leadframe.
As shown in FIGS. 3 and 4, there is shown only a region of a prior art leadframe 1 corresponding to a single semiconductor device. However, the leadframe 1 actually has a sufficient length for making a plurality of such semiconductor devices.
The leadframe 1 has a square island 2 generally at the widthwise center of the leadframe. The leadframe 1 further comprises four integral bridging legs 3a-3d extending radially inward for integral connection to the respective four corners of the island 2, and a multiplicity of integral leads 4 extending radially inwardly toward but spaced from the island 2 between the respective bridging legs 3a-3d.
The island 2 is used for bonding a semiconductor chip 5 which has a multiplicity of connection pads (electrode pads) electrically connected to the resepctive leads 4 through metal wires 6. The semiconductor chip 5 together with the leads 4 and wires 6 is enclosed in a molded resin package 7. This package may be formed by using a mold which has a gate 8 located at one corner of the mold cavity for injecting a fluid resin material, as indicated by arrow A in FIG. 3.
According to the prior art arrangement described above, the leads 4 between the respective bridging legs 3a-3d have their respective tips arranged on a line which is parallel to a corresponding side of the island 2 or semiconductor chip 5. Thus, in order to increase the number of leads while providing a predetermined pitch between the leads (as required for enabling wire bonding while preventing shorting therebetween), it is necessary to increase the spacing S (see FIG. 4) between the tip of each lead and the corresponding side of the chip 5. As a result, the wires 6 close to each bridging leg 3a-3d on both thereof must be inevitably rendered long.
On the other hand, it has been found that the wires 6 close to the bridging leg 3a where the gate 8 is formed are more influenced by a force component of the fluid resin injection pressure transverse to these wires than the other wires at the time of molding the resin package 7. Thus, if the wires 6 close to the bridging leg 3a are long, it is feared that they may be forcibly curved into shorting contact with the neighboring leads under the pressure of the injected resin fluid, thereby resulting in an unacceptable product quality.